Authorities have documented an uptick in campus attacks in the last couple decades, but don't have an explanation why

Receive the latest local updates in your inbox

A stabbing rampage left more than a dozen people hurt on the CyFair campus of Lone Star College in Houston.

The stabbing rampage that injured more than a dozen people at Lone Star College on Tuesday put the school on a long list of violent attacks on American campuses, crimes that have been occurring with increasing frequency.

The earliest recorded deadly campus attack was a 1909 murder-suicide in Boston. But the uptick didn't begin until the latter part of the century.

The incidents that marked the modern era of violent campus attacks were the 1966 sniper killings at the University of Texas that left 15 dead and 32 wounded and the 1970 Kent State shootings by national guardsmen that killed four students and wounded nine. Nearly four decades later came history's worst school shooting: the 2007 Virginia Tech massacre that left 32 people dead and injured another 17.

The Virginia Tech killings prompted a long spell of national soul searching similar to what followed December's massacre at Sandy Hook Elementary School in Newtown, Conn. In the wake of the 2007 rampage, federal authorities examined 272 documented "targeted" violent attacks—fatal and non-fatal—on college campuses since 1900, and found a disturbing trend: 60 percent of them had occurred since 1990.

The 2008 federal study found that shootings were the most prevalent method of campus attacks, accounting for 54 percent of them. Next were stabbings, at 21 percent.

The report's authors—officials at the FBI, Secret Service and Department of Education—could not determine a cause for the increase. They ventured that the trend could have something to do with increased college enrollment, and more intense media coverage.

Since April 2007, there have been about 30 more violent campus attacks, including two smaller incidents at Virginia Tech, according to the consulting firm National School Safety and Security Services and media accounts. The 2012 tally includes the seven killed and three hurt at Oikos University in Oakland and three killed at Casper College in Wyoming.

In January, three people were wounded at a shooting at Lone Star College. Tuesday's stabbing attack occurred on a different campus of the college, and did not appear related to the January shooting.